Effective control and application of power is a major consideration in the development of consumer and industrial electronic products. One form of power conversion system employed today is a resonant converter, which is comprised of inductor-capacitor (L-C) networks of various configurations for shaping the waveform of either the current or the voltage being driven across a given switching element of the circuitry. While various electrical components may be used in the design of a resonant converter, synchronous rectifiers (SRs) are often used in applications that require conversion of alternating current (AC) to direct current (DC). SRs are electronic components encompassing a diode and a transistor (typically a power metal-oxide-semiconductor field-effect transistor (MOSFET)) connected in parallel. In operation, when the diode is forward-biased, the transistor is turned on to reduce the voltage drop. This minimizes the overall energy loss within the circuitry, ensuring that power is persistently switched on or off during and throughout the circuit's operation.
In some instances, the SRs are turned on by a secondary driver of the resonant circuit earlier than the primary driver for the other switching elements of the circuit to reduce the loss caused by the current flowing through the body diodes of the SRs. Consequently, this introduces a phase delay between the secondary driver of the SRs and the primary driver of the other switching elements of the resonant converter, wherein the driver of the SRs is ahead of that of the corresponding switching elements a diode-conducting period/phase degree that the body diodes conduct before the corresponding primary switching elements. Whether SRs are used or not, the resonant converter encounters a problem that the DC voltage gain (nVo/Vin) is non-monotonic within the circuitry, where multiple different frequency levels may correspond to the exact same gain level. Furthermore, the DC gain cannot be zero or near to zero no matter how to vary the frequency of the resonant converter. These diminish the converters 101 effectiveness as a power control mechanism within an electronic application or consumer device; where it is desired to achieve a stable, monotonic (e.g., linear) gain response along with frequency/shifted phase angle or other variable to prevent component damage, and to obtain a zero DC gain to get a smoothing startup waveform from zero voltage.